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feat: In cluster dialer to proxy TCP connections to unexposed services #688
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,324 @@ | ||
| package k8s | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "context" | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
| "net" | ||
| "time" | ||
|
|
||
| coreV1 "k8s.io/api/core/v1" | ||
| metaV1 "k8s.io/apimachinery/pkg/apis/meta/v1" | ||
| "k8s.io/apimachinery/pkg/fields" | ||
| "k8s.io/apimachinery/pkg/util/rand" | ||
| "k8s.io/apimachinery/pkg/watch" | ||
| "k8s.io/client-go/kubernetes" | ||
| "k8s.io/client-go/kubernetes/scheme" | ||
| v1 "k8s.io/client-go/kubernetes/typed/core/v1" | ||
| restclient "k8s.io/client-go/rest" | ||
| "k8s.io/client-go/tools/remotecommand" | ||
| ) | ||
|
|
||
| const ( | ||
| socatImage = "quay.io/mvasek/socat:alpine" | ||
| ) | ||
|
|
||
| type ContextDialer interface { | ||
| DialContext(ctx context.Context, network string, addr string) (net.Conn, error) | ||
| Close() error | ||
| } | ||
|
|
||
| // NewInClusterDialer creates context dialer that will dial TCP connections via POD running in k8s cluster. | ||
| // This is useful when accessing k8s services that are not exposed outside cluster (e.g. openshift image registry). | ||
| // | ||
| // Usage: | ||
| // | ||
| // dialer, err := k8s.NewInClusterDialer(ctx) | ||
| // if err != nil { | ||
| // return err | ||
| // } | ||
| // defer dialer.Close() | ||
| // | ||
| // transport := &http.Transport{ | ||
| // DialContext: dialer.DialContext, | ||
| // } | ||
| // | ||
| // var client = http.Client{ | ||
| // Transport: transport, | ||
| // } | ||
| func NewInClusterDialer(ctx context.Context) (ContextDialer, error) { | ||
| c := &contextDialer{} | ||
| err := c.startDialerPod(ctx) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return c, nil | ||
| } | ||
|
|
||
| type contextDialer struct { | ||
| coreV1 v1.CoreV1Interface | ||
| restConf *restclient.Config | ||
| podName string | ||
| namespace string | ||
| } | ||
|
|
||
| func (c *contextDialer) DialContext(ctx context.Context, network string, addr string) (net.Conn, error) { | ||
| if !(network == "tcp" || network == "tcp4" || network == "tcp6") { | ||
| return nil, fmt.Errorf("unsupported network: %q", network) | ||
| } | ||
|
|
||
| execDone := make(chan struct{}) | ||
| pr, pw, conn := newConn(execDone) | ||
|
|
||
| go func() { | ||
| defer close(execDone) | ||
| errOut := bytes.NewBuffer(nil) | ||
| err := c.exec(addr, pr, pw, errOut) | ||
| if err != nil { | ||
| err = fmt.Errorf("failed to exec in pod: %w (stderr: %q)", err, errOut.String()) | ||
| _ = pr.CloseWithError(err) | ||
| _ = pw.CloseWithError(err) | ||
| } | ||
| }() | ||
|
|
||
| return conn, nil | ||
| } | ||
|
|
||
| func (c *contextDialer) Close() error { | ||
| ctx, cancel := context.WithTimeout(context.Background(), time.Minute*1) | ||
| defer cancel() | ||
| delOpts := metaV1.DeleteOptions{} | ||
|
|
||
| return c.coreV1.Pods(c.namespace).Delete(ctx, c.podName, delOpts) | ||
| } | ||
|
|
||
| func (c *contextDialer) startDialerPod(ctx context.Context) (err error) { | ||
| cliConf := GetClientConfig() | ||
| c.restConf, err = cliConf.ClientConfig() | ||
| if err != nil { | ||
| return | ||
| } | ||
|
|
||
| err = setConfigDefaults(c.restConf) | ||
| if err != nil { | ||
| return | ||
| } | ||
|
|
||
| client, err := kubernetes.NewForConfig(c.restConf) | ||
| if err != nil { | ||
| return | ||
| } | ||
| c.coreV1 = client.CoreV1() | ||
|
|
||
| c.namespace, err = GetNamespace("") | ||
| if err != nil { | ||
| return | ||
| } | ||
|
|
||
| pods := client.CoreV1().Pods(c.namespace) | ||
|
|
||
| c.podName = "in-cluster-dialer-" + rand.String(5) | ||
|
|
||
| defer func() { | ||
| if err != nil { | ||
| c.Close() | ||
| } | ||
| }() | ||
|
|
||
| pod := &coreV1.Pod{ | ||
| ObjectMeta: metaV1.ObjectMeta{ | ||
| Name: c.podName, | ||
| Labels: nil, | ||
| Annotations: nil, | ||
| }, | ||
| Spec: coreV1.PodSpec{ | ||
| Containers: []coreV1.Container{ | ||
| { | ||
| Name: c.podName, | ||
| Image: socatImage, | ||
| Stdin: true, | ||
| Command: []string{"sleep", "infinity"}, | ||
| }, | ||
| }, | ||
| DNSPolicy: coreV1.DNSClusterFirst, | ||
| RestartPolicy: coreV1.RestartPolicyNever, | ||
| }, | ||
| } | ||
| creatOpts := metaV1.CreateOptions{} | ||
|
|
||
| ready := c.podReady(ctx) | ||
|
|
||
| _, err = pods.Create(ctx, pod, creatOpts) | ||
| if err != nil { | ||
| return | ||
| } | ||
|
|
||
| select { | ||
| case err = <-ready: | ||
| case <-ctx.Done(): | ||
| err = ctx.Err() | ||
| case <-time.After(time.Minute * 1): | ||
| err = errors.New("timeout") | ||
| } | ||
|
|
||
| if err != nil { | ||
| err = fmt.Errorf("failed to start dialer container: %w", err) | ||
| } | ||
|
|
||
| return err | ||
| } | ||
|
|
||
| func (c *contextDialer) exec(hostPort string, in io.Reader, out, errOut io.Writer) error { | ||
|
|
||
| restClient := c.coreV1.RESTClient() | ||
| req := restClient.Post(). | ||
| Resource("pods"). | ||
| Name(c.podName). | ||
| Namespace(c.namespace). | ||
| SubResource("exec") | ||
| req.VersionedParams(&coreV1.PodExecOptions{ | ||
| Command: []string{"socat", "-", fmt.Sprintf("TCP:%s", hostPort)}, | ||
| Container: c.podName, | ||
| Stdin: true, | ||
| Stdout: true, | ||
| Stderr: true, | ||
| TTY: false, | ||
| }, scheme.ParameterCodec) | ||
|
|
||
| executor, err := remotecommand.NewSPDYExecutor(c.restConf, "POST", req.URL()) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| return executor.Stream(remotecommand.StreamOptions{ | ||
| Stdin: in, | ||
| Stdout: out, | ||
| Stderr: errOut, | ||
| Tty: false, | ||
| }) | ||
| } | ||
|
|
||
| func (c *contextDialer) podReady(ctx context.Context) (errChan <-chan error) { | ||
| d := make(chan error) | ||
| errChan = d | ||
|
|
||
| pods := c.coreV1.Pods(c.namespace) | ||
|
|
||
| nameSelector := fields.OneTermEqualSelector("metadata.name", c.podName).String() | ||
| listOpts := metaV1.ListOptions{ | ||
| Watch: true, | ||
| FieldSelector: nameSelector, | ||
| } | ||
| watcher, err := pods.Watch(ctx, listOpts) | ||
| if err != nil { | ||
| return | ||
| } | ||
|
|
||
| go func() { | ||
| defer watcher.Stop() | ||
| ch := watcher.ResultChan() | ||
| for event := range ch { | ||
| pod := event.Object.(*coreV1.Pod) | ||
|
|
||
| if event.Type == watch.Modified { | ||
| for _, status := range pod.Status.ContainerStatuses { | ||
| if status.Ready { | ||
| d <- nil | ||
| return | ||
| } | ||
| if status.State.Waiting != nil { | ||
| switch status.State.Waiting.Reason { | ||
| case "ErrImagePull", | ||
| "CreateContainerError", | ||
| "CreateContainerConfigError", | ||
| "InvalidImageName", | ||
| "CrashLoopBackOff", | ||
| "ImagePullBackOff": | ||
| d <- fmt.Errorf("reason: %v, message: %v", | ||
| status.State.Waiting.Reason, | ||
| status.State.Waiting.Message) | ||
| return | ||
| default: | ||
| continue | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| }() | ||
|
|
||
| return | ||
| } | ||
|
|
||
| func setConfigDefaults(config *restclient.Config) error { | ||
| gv := coreV1.SchemeGroupVersion | ||
| config.GroupVersion = &gv | ||
| config.APIPath = "/api" | ||
| config.NegotiatedSerializer = scheme.Codecs.WithoutConversion() | ||
|
|
||
| if config.UserAgent == "" { | ||
| config.UserAgent = restclient.DefaultKubernetesUserAgent() | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| type addr struct{} | ||
|
|
||
| func (a addr) Network() string { | ||
| return "pod-stdio" | ||
| } | ||
|
|
||
| func (a addr) String() string { | ||
| return "pod-stdio" | ||
| } | ||
|
|
||
| type conn struct { | ||
| pr *io.PipeReader | ||
| pw *io.PipeWriter | ||
| execDone <-chan struct{} | ||
| } | ||
|
|
||
| func (c conn) Read(b []byte) (n int, err error) { | ||
| return c.pr.Read(b) | ||
| } | ||
|
|
||
| func (c conn) Write(b []byte) (n int, err error) { | ||
| return c.pw.Write(b) | ||
| } | ||
|
|
||
| func (c conn) Close() error { | ||
| err := c.pw.Close() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to close writer: %w", err) | ||
| } | ||
| <-c.execDone | ||
| err = c.pr.Close() | ||
| if err != nil { | ||
| return fmt.Errorf("failed to close reader: %w", err) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func (c conn) LocalAddr() net.Addr { | ||
| return addr{} | ||
| } | ||
|
|
||
| func (c conn) RemoteAddr() net.Addr { | ||
| return addr{} | ||
| } | ||
|
|
||
| func (c conn) SetDeadline(t time.Time) error { return nil } | ||
|
|
||
| func (c conn) SetReadDeadline(t time.Time) error { return nil } | ||
|
|
||
| func (c conn) SetWriteDeadline(t time.Time) error { return nil } | ||
|
|
||
| func newConn(execDone <-chan struct{}) (*io.PipeReader, *io.PipeWriter, conn) { | ||
| pr0, pw0 := io.Pipe() | ||
| pr1, pw1 := io.Pipe() | ||
| rwc := conn{pr: pr0, pw: pw1, execDone: execDone} | ||
| return pr1, pw0, rwc | ||
| } | ||
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@rhuss @markusthoemmes is there a way to make pod to be automatically delete upon completion?
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You can do this if you are using a higher-level abstraction like
DeploymentorReplicaSetif you want them to manage the lifecycle of your pod, otherwise, you have to do it on your own.There was a problem hiding this comment.
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btw, what do you mean with 'upon' completion ? When all containers in the pod stop ?
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Yes, when all processes exited.
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If the app for some reason crashes the
Close()may not be called so there would be dangling completed pods.